1. Technical Field
The invention relates generally to the field of printing and printing devices. More specifically, the invention relates to printing on devices that have the capability to use white ink as a printing color.
2. Description of the Related Art
Presently, to print on media whose color is other than white or near white, -a white ink separation is printed first. Options may include printing the white ink separation as a full tone layer (100%) followed by printing additional inks on top of the full tone layer or manually creating the white ink separation as a spot color separation in the job creation process.
The white layer may be generated automatically by performing a mathematical function of the process output colors CMYK. For instance, white may be created wherever any of C, M, Y, or K is unequal to zero. According to this process, a white background is created behind the printed area and the process leaves the unprinted area free of white. That is, in accordance with the approach of printing a white ink separation as a full tone layer, when it is desired to have a printout with white ink, then white is printed as a complete white layer, 100% white, that is effectively a complete coating of the substrate on which the image is to be printed. After printing 100% white on the substrate, CMYK inks are printed on top of the white layer to create the image. It should be appreciated that other inks such as red, orange, green, blue, silver, gold, etc., may print on top of the white later as well, e.g. depending on the type of the printing device.
The second approach includes creating an International Color Consortium (ICC) profile with five channels. For purposes of discussion herein, an ICC profile is a file or set of data that applies values to maintain color consistency from device to device. The International Color Consortium is the forum responsible for such printing standards. These five channels are C, M, Y, K, and white. An ICC profile with more than the process colors, CMYK, may be referred to as an N-color profile.
To create an ICC profile, a color profiling application may be required to create such type of multi-channel profile. Additionally it may also be necessary for a user to generate a particular set of charts and print and measure such charts to create the ICC profile. The process involves printing special color charts on the given media on the particular printer. Color patches on such printed charts are measured subsequently using a measuring device such as a spectrophotometer. There are many applications in the market that are capable of creating CMYK based ICC profiles, however only few are able to build an ICC profile that contains a white channel in addition to the other colors.
Further these approaches and other existing techniques may include creating a white ink layer or image based on empirical methods by in-situ measurements of the change in color depth with varying densities of white-ink for each of the possible CMYK combinations. Other methods may determine the white ink heuristically, e.g. depending on a set of if-then rules based on the combination of media color and the regions within the image.